It is proposed to develop a multiplex cytotoxicity assay on electronic microchips, microtransponders. Each microtransponder is composed of photocells, antenna and memory to store information that identifies the specific features of the biological material, such as cells, attached to the chip. In the assay, cells are stained with a fluorescent dye and fluorescence intensity is quantified in a flow-based instrument, which also reads the ID of the chip. The microchips, as well as the instrumentation to read the chips, have been built by PharmaSeq. PharmaSeq has also demonstrated several nucleic acid-based and protein-based assays on microtransponders. The present project aims at testing feasibility of a drug screen assay in which cells are grown on microtransponders in the presence of a chemical compound. Depending on the type of compound and its concentration, cell growth may be inhibited or even arrested. The fluorescence intensity from the microtransponder provides information about the potency of the drug. Specifically, the main three objectives of the Phase I work are: (a) to determine the optimal conditions for growing mammalian cells attached to microtransponders and to test adherence of cells to their surfaces; (b) to develop an assay for intracellular nucleic acids in the cells immobilized on microtransponders and show that the PharmaSeq flow reader instrument can be used to measure fluorescence of individual microtransponders carrying the cells; and (c) to demonstrate an assay in which cell growth on microtransponders is inhibited in the presence of cytostatic/cytotoxic agents. Six anti-cancer cell lines and four chemical compounds will be tested. The benefits of the program involve the advancement of cell-based assay technology, acceleration of drug discovery programs in research laboratories and pharmaceutical industry, and cost savings.